The present invention relates to optical radar, particularly to a radar technology that uses lasers for purposes of generating range images, to be used in the navigation of aircraft or, more generally, general aerospace crafts and vehicles.
Range images are defined by images having or being composed of image points the content of which is not indicative of reflected energy but is representative of the distance of that point which produced the reflection from say the range finder camera or reference plane. In the case of a black and white range image or, preferably, of a range image having several gray stages, it is customary to represent an object point that is very close in a rather dark fashion while an object point that is quite far is relatively brightly imaged. Range finder images of this kind are used for example for navigation or updating or correction of navigation and navigational information in aerospace vehicles.
These range finder images represent the area or territory passed over by the vehicle and the representation is subject to a line-by-line scan. For purposes of obtaining this kind of scan it is customary to use a mechanically moved, scanning part such as pivoting mirrors or rotating polygon mirrors or the like. These movable components deflect the laser beam in a line scan pattern and direct the beam particularly down to ground while a detector repsonds to the returning deflection. Basically this kind of an arrangement is sound but has the drawback that mechanically movable parts simply limit the use life of the equipment; also storage time (inventory) is quite limited, and it was found moreover that for high speed aircraft this kind of scanning is actually rather poorly suitable. As state of the art please refer to German applications 292095 and 2909090 which are based on Japanese patent applications for which there may be U.S.-counter parts.